The choice of valve for a particular application depends on various factors such as the fluid flow rate, the process temperatures and pressures,MUD VALVES and whether the fluid is corrosive or abrasive. An important design consideration for safety is the maximum pressure and temperature of the flowing fluid as this will dictate a safe thickness for the body material and may determine which materials can be used.Needle Valves The capacity of a valve is measured in Cv, Kv or Av and can be determined experimentally for a valve by testing it, for example by measuring the amount of water that flows through it at a certain pressure differential across the valve.
The valve needed for an application will depend on whether the fluid is a liquid, gas or multi-phase fluid and on the properties of the fluid. Normally a number of process conditions - each of which will specify the inlet and outlet pressure, temperature, flow rate and maybe other fluid details - are used to calculate a required capacity, and to estimate the noise and the cavitation. Ball ValvesValves often have interchangeable internal components, called the trim, which can be selected to modify the valve to accommodate particular process conditions. For example perforated trim can be used to reduce the noise level by splitting the flow into multiple independent streams.
Due to the complexity of the fluid flow, noise and cavitation calculations often required to size and select an appropriate control valve many manufacturers provide a computer program to assist their customers. For example Severn Glocon and Dresser provide downloadable sizing programs. A small number of software companies have specialist products for this market such as Conval and the Millstream Software Valve Sizing Program.

MORE NEWS

2011-11-15

Back